Add a basic readme to point people elsewhere

Author: briandfoy

README.md

@@ -0,0 +1,5 @@
+This is a historical repo. The _cpan(1)_ script now lives in the [main
+CPAN.pm repo](https://github.com/andk/cpanpm).
+
+If you really want to use this you'll have to find some `die` statements
+I left in the code. There's no support for this repo.